I've actually got this working now! Sheesh, lots of dependancies, although that was the first time I have used cpan - updates things nice and easily.
I had to use
force install DBD::mysql because for some reason it couldn't connect to mysql with the username and password it was trying with during testing.
Few tweaks and typo removals means I should now be working ok:
http://forums.utassault.net/mrtg/vb/
Many thanks for this hack.